42 results about "Circumferential strain" patented technology

The invention provides a corrugated pipe forming springback control method and die based on stress regulation and control, and relates to the technical field of metal processing. The method comprises the following steps: obtaining a circumferential strain increment expression according to a material bending deformation principle; a plastic strain increment expression, a plastic stress differential equation and a circumferential strain increment expression are combined to obtain a circumferential stress and axial stress relational expression, and according to the circumferential stress and axial stress relational expression, a relation curve with the circumferential compression dependent variable as an independent variable and the ratio of the axial stress to the pre-compression as a dependent variable is obtained; after the pipe blank is bent and deformed, the wave troughs can move towards the axis of the pipe blank in the radial direction of the pipe blank to achieve radial shrinkage of the wave troughs, so that the circumferential stress of the wave troughs is increased, the axial stress difference of the inner surface and the outer surface is reduced, then the axial stress of the corrugated pipe is reduced, and the axial springback of the corrugated pipe is effectively controlled.

The invention relates to the technical field of bridge load tests, and provides a bridge load test crack increment change observation method and system, and the method comprises the steps: collecting prestressing tendon circumferential strain distribution data and dual-wavelength strain response data; calculating an interface bonding stiffness change parameter; pre-stress modulation effect compensation and polar coordinate system conversion are carried out on the strain response data and the rigidity change parameters, and micro-crack characteristic signals are obtained; load data and beam group arrangement parameters are collected, and a micro-crack propagation prediction model is established in combination with the interface bonding stiffness change parameters; inputting the micro-crack characteristic signal into a micro-crack propagation prediction model, and outputting a micro-crack development trend prediction result; and adjusting sampling parameters of a dual-wavelength time division multiplexing algorithm and characteristic extraction parameters of prestress modulation effect compensation according to a micro-crack development trend prediction result. According to the invention, the precision of observing the increment change of the micro-crack in the bridge load test is improved, and the automatic monitoring and prediction of the micro-crack of the prestressed concrete bridge are realized.

The invention discloses a tire grounding mark length testing method and device, and relates to the field of tire grounding mark length testing. According to the method, the grounding data and the circumferential strain curve of the tire are obtained through the strain waveform data of the tire movement in combination with the flexible tire body model, and then the grounding angle of the tire is obtained, so that the grounding mark length of the tire is determined in combination with the geometric radius of the tire. By exploring the relation between the grounding angle and the grounding mark length in the tire movement process and excavating the coupling relation between radial deformation and tangential deformation of the tire body circular ring, the accuracy of the grounding mark length is improved. Through the strain waveform data of the tire and by taking the circumferential strain as a medium, the calculation step of the length of the grounding mark is simplified, and the testing efficiency of the length of the grounding mark is improved, so that the performance of the tire can be evaluated and improved based on the length of the grounding mark of the tire, and the driving safety and performance of an automobile are improved.

The invention discloses a correction method for solving a drilling hole eccentric error in hollow inclusion crustal stress measurement. The correction method comprises the following steps: establishing a geometric simplified model of an eccentric drilling hole based on various parameters required in a confining pressure calibration test; on the basis, a stress calculation graph under bipolar coordinates is established, and hole wall circumferential strain is obtained based on an eccentric rock core hole wall circumferential stress calculation formula and a physical equation; by combining the obtained hole wall strain with the arrangement angle of a strain rosette of the hollow inclusion meter and a confining pressure calibration formula, a correction method for the elastic modulus of the rock before and after eccentricity is provided, the elastic modulus E1 of the rock measured by the confining pressure calibration during eccentricity is corrected, and a rock elastic modulus correction value E0 is obtained; substituting the corrected elastic modulus value into a correction coefficient calculation formula to obtain each corrected ki coefficient value; and finally, the E0 and the corrected ki are substituted into a conventional principal stress calculation process, so that six corrected crustal stress components and three corrected principal stress sizes and directions are obtained.

The invention discloses a strain analysis method and system based on heart CT data. The method comprises the following steps: segmenting an original heart CT image through an image segmentation network structure to obtain a segmentation result; inputting the segmentation result into a pre-trained key point detection model to obtain a plurality of key points; determining a ventricular long axis and a ventricular short axis according to the plurality of key points, and obtaining a segmentation result; registering the heart mask image by using an image registration framework to obtain a deformation field of myocardial movement from the end stage of myocardial diastole to the end stage of myocardial systole; and performing strain analysis according to the segmentation result and the deformation field, and calculating to obtain the overall radial strain, the overall longitudinal strain and the overall circumferential strain of the heart. The myocardial strain analysis is realized through the myocardial strain analysis framework, different segments of the myocardial can be analyzed, various parameter indexes are obtained, and efficient processing and accurate analysis of heart CT data are realized.

This invention discloses a method for determining the optimal stable cross-section of a large-span, flat cavern, relating to the fields of geotechnical engineering and underground structure design. The method first establishes a parametric geomechanical model using the cavern span L, crown rise S, and sidewall height H as control parameters. Second, based on the mechanical properties of the surrounding rock, a critical stability criterion is defined, with the comparison of circumferential strain and ultimate strain as its core. Then, using a particle swarm optimization algorithm, under preset geometric constraints and with the critical stability criterion as boundary conditions, a multi-objective iterative optimization calculation is performed on the parameter set (L, S, H). Finally, the target parameter set (Lf, Sf, Hf) that satisfies the critical stability state and has optimal geometric dimensions is output as the optimal stable cross-section solution. This invention automates and optimizes cross-section design, enabling the search for the most economical and efficient cavern cross-section shape while ensuring the self-stability of the surrounding rock, effectively overcoming the shortcomings of traditional design methods that rely on experience and are difficult to optimize.

The invention belongs to the technical field of geotechnical engineering testing, particularly relates to a method for determining composite modulus of waste whole-tire reinforced soil, and aims to solve the problem of data distortion in traditional testing. Comprising the following steps: carrying out a uniaxial tensile test on a waste whole tire to obtain a tire tensile modulus for circumferential stress analysis; the method comprises the following steps: preparing a waste whole tire-filler soil composite sample, carrying out an unconfined compression test, arranging a linear variable differential displacement meter in the diameter direction of the tire to monitor the overall diameter change, and pasting a resistance strain gauge on the inner wall of the tire to measure the local circumferential strain; and calibrating the reading of the resistance strain gauge by using the monitoring result of the linear variable differential displacement meter to obtain calibrated circumferential strain data. And on the basis of a circumferential tension theory, equivalent confining pressure increment provided by the tire to the filler soil is calculated for the obtained calibrated circumferential strain data. And substituting the obtained tire equivalent confining pressure increment into the relationship between the modulus of the filler soil and the confining pressure, and calculating and determining the composite modulus of the waste whole tire reinforced soil.

The invention discloses a well cementation cement sheath integrity failure evaluation method and system based on strain measurement, and relates to the technical field of oil drilling engineering well cementation, and the method comprises the steps: carrying out the parameter initialization of a shaft simulation system, and maintaining a to-be-evaluated cement sheath; adjusting the in-pipe pressure value of the cement sheath to be evaluated after maintenance to change along with time based on a shaft simulation system, and acquiring time-varying data of an end face radial strain value of the cement sheath to be evaluated and time-varying data of an inner wall circumferential strain value; respectively generating an in-pipe pressure value change curve, an end face radial strain value change curve and an inner wall circumferential strain value change curve; respectively calculating a first curve goodness of fit and a second curve goodness of fit; and based on the first curve goodness of fit and the second curve goodness of fit, evaluating the integrity failure of the cement sheath to be evaluated. Whether the integrity of the cement sheath fails or not can be judged by analyzing the strain of the cement sheath.

The application discloses a residual stress detection method in an expansion pipe experimental comprehensive test system. The expansion pipe experimental comprehensive test system is mainly composed of a hydraulic system, an expansion pipe, an expansion cone, a strain collection system, an expansion pipe post-expansion shearing device, an expansion pipe post-expansion anti-external extrusion device and the residual stress detection method. The residual stress detection method is characterized in that the expansion cone is driven to expand the expansion pipe in the axial direction through the hydraulic system, the axial and circumferential strains of the expansion pipe wall during the expansion are collected, the moving distance of the expansion cone is collected in real time through a displacement sensor, the pressure value of the oil pressure of the compression system is collected through a pressure sensor, and then the driving force value during the expansion process is calculated; the post-expansion expansion pipe is subjected to shearing and pressure extrusion resistance experiments, and the residual stress value of the pipe body is detected by using the ring cutting method and the strip cutting method. The residual stress detection method in the expansion pipe experimental comprehensive test system can comprehensively improve the expansion pipe experimental efficiency and the data collection accuracy, and provides reliable data support for the expansion pipe expansion mechanism research.

The application provides a containment concrete temperature strain correction method, device, equipment and medium, and relates to the technical field of nuclear power containment concrete strain correction. The method comprises the following steps: collecting temperature information and strain information of the containment to form a sample set; selecting a preset period of sample sets to form an analysis sample set; based on the assumption that the temperature of the containment cylinder is linearly distributed, the circumferential strain and vertical strain caused by temperature change are obtained; the analysis sample set is fitted by least squares nonlinear fitting to obtain the thermal expansion coefficient temperature correction coefficient of the concrete; and the thermal expansion coefficient and temperature correction coefficient of the concrete obtained are substituted into the formula to obtain the circumferential strain and vertical strain caused by temperature change. The method can accurately evaluate the safety index of the containment, master the actual state of the containment, and optimize the maintenance cost and resources.

The invention relates to the technical field of strain measurement, in particular to a device for measuring micro circumferential strain of a concrete cylinder test piece. In order to solve the problem that the existing method for measuring the micro circumferential strain of the test piece is difficult to test the micro circumferential strain of the test piece, the invention provides a novel device for measuring the micro circumferential strain of the concrete cylinder test piece, which comprises a first arc-shaped frame and a second arc-shaped frame, the first arc-shaped frame and the second arc-shaped frame are each provided with an annular supporting part, the two annular supporting parts are distributed in a bilateral symmetry mode, a first extending part is fixed to the front end of the first arc-shaped frame, a second extending part is fixed to the front end of the second arc-shaped frame, and a clamping spring is arranged between the first extending part and the second extending part. The left side portion of the second extending portion extends leftwards to form a connecting portion, a supporting leg is fixed to the connecting portion, and a displacement sensor is further fixed to the connecting portion. The device is simple in structure, low in manufacturing cost and convenient to use.

This invention belongs to the field of geotechnical engineering testing technology, specifically relating to a method for determining the composite modulus of waste tire reinforced soil, aiming to solve the problem of data distortion in traditional testing. The method includes conducting uniaxial tensile tests on waste tires to obtain the tire tensile modulus for circumferential stress analysis. Waste tire-fill soil composite samples are prepared and subjected to unconfined compression tests. A linear variable differential displacement gauge is placed along the tire diameter direction to monitor the overall diameter change. Resistance strain gauges are attached to the inner wall of the tire to measure local circumferential strain. The readings of the resistance strain gauges are calibrated using the monitoring results of the linear variable differential displacement gauge to obtain calibrated circumferential strain data. Based on circumferential tension theory, the equivalent confining pressure increment provided by the tire to the filler soil is calculated from the obtained calibrated circumferential strain data. The obtained equivalent confining pressure increment is substituted into the relationship between the modulus of the filler soil and the confining pressure to calculate and determine the composite modulus of waste tire reinforced soil.

This optical fiber measurement device (100) for monitoring the axial force of a bolt is provided with: an optical fiber (23) for measuring the strain of an object to be measured; an optical fiber attachment fixing body (25) having an optical fiber attachment nut (21S) to which an optical fiber (23) is attached by changing the shape of the outer peripheral portion of the nut (21) related to at least one combination of the plurality of sets of bolts (20) and nuts (21); and an optical fiber strain distribution measurement unit (24) that measures the circumferential strain distribution of the optical fiber attachment nut (21S) generated by the bolt axial force along the optical fiber (23) attached to the outer peripheral surface of the optical fiber attachment nut (21S), and that measures the circumferential strain and the circumferential strain distribution of the optical fiber attachment nut (21S) in advance by means of the optical fiber strain distribution measurement unit (24). An optical fiber (23) is installed at a specified axial position corresponding to the circumferential strain value or the circumferential strain distribution measured in advance, and the bolt axial force is monitored.

The present invention provides a bellows forming springback control method and mold based on stress regulation, relating to the field of metal processing technology. The method comprises obtaining an expression for the circumferential strain increment based on the principle of material bending deformation; simultaneously establishing an expression for the plastic strain increment, a plastic stress differential equation, and an expression for the circumferential strain increment to obtain an expression for the relationship between the circumferential stress and the axial stress; and, based on the expression for the relationship between the circumferential stress and the axial stress, obtaining a relationship curve with the circumferential compression strain as the independent variable and the ratio of the axial stress to the stress before compression as the dependent variable. After the tube is bent and deformed, the trough can be moved radially toward the axis of the tube along the radial direction of the tube to achieve radial contraction of the trough, thereby increasing the circumferential stress of the trough and reducing the axial stress difference between the inner and outer surfaces, thereby reducing the axial stress of the bellows and effectively controlling the axial springback of the bellows.

The application discloses an alloy compression deformation experiment method for obtaining a circumferential strain gradient, and relates to the technical field of alloy material deformation experiments.The working surface of a compression experiment mold or the end surface of a cylindrical sample is processed into a wedge-shaped structure which is mirror-symmetric about the plane where the central axis of the cylindrical sample is located, so that the cylindrical sample has different compression deformation spaces at different circumferential positions during axial compression, and thus the strain gradient distributed along the circumference is obtained on a single sample; by comparing the deviation of nominal strain calculation and finite element simulation, the strain control accuracy of different schemes can be quantitatively evaluated, and then the finally adopted experiment scheme is determined.The application effectively reduces the interference of defect factors such as radial segregation and inclusions on the experiment results, guarantees that the experiment results are affected by a single variable of strain, and significantly improves the accuracy of experiment data.

The application belongs to the technical field of long-term drift suppression of fiber-optic gyroscope zero bias and scale factor, and particularly relates to a long-term drift suppression method for equivalent sensitive area of a fiber coil. A homogenization, de-homogenization analysis idea and a finite element analysis approach are adopted to establish, verify and calibrate thermodynamic parameters of each non-metallic material of the fiber coil. A mathematical model of long-time drift of circumferential strain, radial strain and three-dimensional stress of a micro-element section of the fiber coil with time, temperature and other environmental conditions is calculated to obtain long-time drift of effective refractive index of each micro-element section. Finally, average long-time drift and dispersion characteristics of the effective refractive index of the fast axis of the fiber coil are obtained, so that long-time drift characteristics of the scale factor of the fiber-optic gyroscope are analyzed. In turn, according to the model, thermodynamic parameters and geometric proportions of each non-metallic material of the fiber coil are optimized to finally realize long-term drift suppression of the equivalent sensitive area of the fiber coil.

The invention discloses a pipe fitting expanding force testing method, which relates to the field of pipe fitting processing, and comprises the following steps: selecting a testing pipe section with the length equal to the expanding step length along the axial direction of a pipe fitting, and selecting the cross section of at least one pipe fitting as a testing section along the axial direction of the testing pipe section, selecting at least two strain measuring points on the outer wall of the pipe fitting at the position of each test section; obtaining the effective contact area of the diameter expanding mold and the inner wall of the test pipe section in the diameter expanding process of the test pipe section; acquiring the circumferential strain of each strain measuring point of the test pipe section in the expanding process; acquiring the circumferential stress at each strain measuring point through the circumferential strain at each strain measuring point; obtaining the expanding pressure of each corresponding strain measuring point through the circumferential stress of each strain measuring point; the average diameter expanding force at all the strain measuring points is obtained through the effective contact area and the diameter expanding pressure at all the strain measuring points, and the average diameter expanding force is the pipe fitting diameter expanding force of the diameter expanding mold on the test pipe section. According to the invention, the accuracy of pipe expanding force testing can be improved.

The invention relates to the technical field of deep hole displacement observation, and discloses an automatic deep hole displacement observation device and method based on stress strain measurement, and the device comprises an observation pipe which is vertically buried in a drill hole; the plurality of strain gauges are arranged on the outer wall of the observation pipe and are used for acquiring axial strain and circumferential strain data in different depths and directions in real time; the data acquisition module is provided with a wireless transmission module and is connected with the strain gauges through the wireless transmission module; a displacement integral algorithm and a finite element model are built in the data processing unit, and the data processing unit is used for calculating the sliding mass displacement and a three-dimensional deformation field; and the monitoring terminal receives and displays the displacement result and the early warning information. According to the invention, the position and deformation of the sliding surface are judged by observing the stress change condition of the pipe wall, and the sliding direction and deformation condition of the landslide are judged. That is to say, stress-strain changes of the pipe wall are observed by monitoring the deep hole, and the sliding direction and deformation condition of the landslide are indirectly obtained by inverting the deformation amount and direction of the slip mass.

The invention belongs to the technical field of underground tension measurement, and particularly relates to a tension sensor measuring circuit and a tensiometer. The device comprises four groups of strain units which are sequentially connected to form a full-bridge circuit, and the strain units on oppositely arranged bridge arms of the full-bridge circuit are respectively a first strain unit and a second strain unit; the two first strain units are arranged in parallel to the axial direction and are used for sensing axial strain; a certain included angle is formed between the two second strain units and the axial direction and is used for sensing circumferential strain; the strain sensitivity coefficient of the second strain unit is different from that of the first strain unit, so that the signal variation of the adjacent first strain unit and second strain unit is the same. The method is used for solving the problems that tension measurement is complex and high in cost, the complex mechanical compensation problem is converted into circuit configuration through source compensation design, and therefore comprehensive optimization is achieved in multiple dimensions such as structural reliability, cost, performance and maintainability, and the method is suitable for petroleum logging scenes with strict requirements.

The application discloses a pipe expanding force testing method, and relates to the field of pipe processing.The method comprises the following steps: selecting a testing pipe section with a length equal to an expanding step along the axial direction of a pipe; selecting at least one cross section of the pipe as a testing cross section along the axial direction of the testing pipe section; selecting at least two strain measuring points on the outer wall of the pipe at the positions of the testing cross sections; obtaining the effective contact area between an expanding die and the inner wall of the testing pipe section during the expanding process; obtaining the circumferential strain of each strain measuring point during the expanding process of the testing pipe section; obtaining the circumferential stress of each strain measuring point through the circumferential strain of each strain measuring point; obtaining the expanding pressure of each strain measuring point through the circumferential stress of each strain measuring point; and obtaining the average expanding force of all the strain measuring points through the effective contact area and the expanding pressure of each strain measuring point, wherein the average expanding force is the pipe expanding force of the expanding die on the testing pipe section.The application can improve the accuracy of pipe expanding force testing.

The invention mainly relates to the technical field of geotechnical engineering tests, and provides a method and a device for calculating deformation parameters of a weathered red-layer soft rock undisturbed sample in order to more accurately determine deformation parameters of red-layer soft rock, the core is that a steel cylinder is adopted to obtain the weathered red-layer soft rock undisturbed sample, the steel cylinder is used as a constraint structure, and the deformation parameters of the weathered red-layer soft rock undisturbed sample are obtained; performing a lateral confinement compression loading test on the sample to obtain the circumferential strain and the axial strain of the outer wall of the steel cylinder in the process; based on the circumferential strain and the axial strain, determining interface axial shear stress between the sample and the inner wall of the steel cylinder, lateral confinement stress of the sample and real axial stress by combining a corrected thick-wall cylinder mechanical model obtained by superposing two groups of loads of the steel cylinder under positive pressure and shearing force; the deformation parameters of the sample are calculated based on the lateral confinement stress and the real axial stress of the sample, the problems of sample preparation failure, structural damage, data distortion and the like caused by the fact that the rock sample must be processed into the standard size in a traditional indoor test are solved, and the deformation parameters of the weathered rock mass can be obtained more accurately.

The invention belongs to the technical field of underground tension measurement, and particularly relates to a tension sensor measuring circuit, a tensiometer and a calculation method. The measuring circuit comprises four groups of strain units, the four groups of strain units are sequentially connected to form a full-bridge circuit, and the strain units on opposite bridge arms of the full-bridge circuit are a first strain unit and a second strain unit respectively; the two first strain units are used for sensing axial strain; each second strain unit comprises at least two strain gauges which are connected in series, at least one strain gauge is obliquely arranged to form a certain included angle with the axial direction and is used for sensing circumferential strain, the other strain gauges are suspended, and the included angle is used for enabling the signal variation of the adjacent first strain unit and second strain unit to be the same. The problem that tension measurement is complex and high in cost is solved, the complex mechanical compensation problem is converted into circuit configuration through source compensation design, and therefore comprehensive optimization is achieved in multiple dimensions such as the structure, reliability, cost, performance and maintainability, and the method is suitable for petroleum logging scenes with strict requirements.

The invention discloses a viscoelasticity-based curved pneumatic muscle mechanism modeling method, which comprises the following steps of: (1) considering a curved pneumatic muscle to be composed of a plurality of infinitesimal elements, performing stress analysis on the infinitesimal elements, and establishing a force balance equation; (2) analyzing the linear pressure of the woven mesh pipe on the elastic hose, and establishing the relationship between the linear pressure and the tensile force of the woven wire; (3) establishing a stress-strain relation of the pneumatic muscle based on a linear viscoelasticity theory; (4) analyzing the balance relation among the air pressure, the circumferential stress and the braided wire tension; (5) establishing a geometrical relationship between the radial displacement and the inner diameter, the circumferential strain, the axial strain, the lift angle of the braided wire and the bending angle; and (6) calculating the model. According to the method, the hysteresis and creep characteristics of the curved pneumatic muscle are described by adopting the linear viscoelastic constitutive relation, a complete mechanism model of the curved pneumatic muscle is established, and a theoretical basis is provided for design, control and optimization of the curved pneumatic muscle.

The present invention discloses a method and device for determining the annular r value of a pipe, and relates to the field of mechanical property testing of pipes; the method comprises: determining the size of an annular sample and cutting the sample from the pipe to be tested; making a speckle or a circular grid on the outer surface of the sample; sleeve the annular sample in the middle position outside the block rigid mold; filling the fluid medium into the liquid bag and controlling the internal pressure, using the uniform load generated by the pressurization of the liquid bag to drive the block rigid mold to move uniformly outward in the radial direction, so that the annular sample undergoes equal-diameter bulging; measuring the width and annular strains of the speckle or grid area on the annular sample; and determining the thickness-wise profile coefficient of the annular pipe according to the width and annular strains. The present invention realizes the direct determination of the annular r value of the pipe by uniformly pressurized equal-diameter bulging, and significantly reduces the influence of friction and greatly improves the measurement accuracy by reasonably designing the width of the sample and the number of rigid mold petals, and designing a lubricating layer between the sample / rigid mold or prefabricating a microstructure on the surface of the rigid mold.

A method for designing a flat device to be thermoformed into a shape-retaining non-flat device using a mold is provided. The flat device comprises two concentric annular layers: a carrier layer, having an outer radius (RCout) and a carrier layer width (WC); and a support layer having a support layer width (WS). The support layer is mechanically attached to the carrier layer wherein an inner distance (GAP) is formed between an inner edge of the carrier layer and an inner edge of the support layer. The method comprises obtaining predetermined values for the outer radius of the carrier layer, the support layer width and the inner distance, obtaining a geometry of the mold, and obtaining material properties of the support layer and the carrier layer. The method further comprises performing at least two simulations of thermoforming a simulated flat device into a non-flat device using the mold, based on the obtained predetermined values, material properties, and geometry of the mold for at least two different carrier layer widths. The method further comprises determining a circumferential strain at an outer edge of the support layer in each of the simulated non-flat devices. The method further comprises determining, based on the determined circumferential strains, a linear relation between the circumferential strain and a dimension ratio defined byratio=(WC-(WS+GAP)) / RCout.The method further comprises determining (1070), based on the determined linear relation, a value (ratioMNB) of the dimension ratio for which the strain is zero and determining, from the dimension ratio for which the strain is zero, the width of the carrier layer in the flat device asWC=ratio*RCout+WS+GAP.

This invention discloses a method for monitoring the overall deformation of tunnels based on distributed optical fiber sensing and complex variable function method, belonging to the field of underground engineering structural health monitoring technology. The method includes: S1, constructing a displacement inversion analytical model: based on the complex variable function theory of elasticity and conformal mapping method, a displacement inversion analytical model for strain-to-displacement conversion is established; S2, distributed strain data acquisition: distributed strain sensing optical fibers are circumferentially deployed on the inner surface of the non-circular tunnel lining, and optical frequency domain reflection technology is used to collect circumferential strain distribution data of the entire cross-section of the non-circular tunnel in real time; S3, strain-displacement conversion calculation: the collected circumferential strain data is input into the displacement inversion analytical model, and the continuous displacement distribution of the inner wall of the non-circular tunnel is inverted through numerical calculation. This method not only accurately captures the details of strain abrupt changes in key parts such as the tunnel arch and corners, but also accurately converts strain data into intuitive displacement information.

The present application relates to the technical fields of strain measurement, in particular to a device for measuring the micro hoop strain of a concrete cylinder specimen. In order to solve the problem that the existing method for measuring the micro hoop strain of a specimen is difficult to test the micro hoop strain of the specimen, a new device for measuring the micro hoop strain of a concrete cylinder specimen is provided, which comprises a first arc-shaped frame and a second arc-shaped frame, and the first arc-shaped frame and the second arc-shaped frame are both provided with a hoop support part, the two hoop support parts are symmetrically distributed left and right, the front end of the first arc-shaped frame is fixed with a first extension part, the front end of the second arc-shaped frame is fixed with a second extension part, a clamping spring is arranged between the first extension part and the second extension part, the left side of the second extension part extends leftward with a connecting part, the connecting part is fixed with a supporting leg, and the connecting part is also fixed with a displacement sensor. The device has simple structure, low manufacturing cost and is convenient to use.

The invention discloses a method for determining an optimal stable section of a large-span flat cavern, and relates to the technical field of geotechnical engineering and underground structure design. The method comprises the following steps: firstly, establishing a parameterized geomechanical model by taking a cavern span L, a vault rise S and a side wall height H as control parameters; secondly, based on the mechanical characteristics of the surrounding rock, defining a stability critical criterion taking the comparison of circumferential strain and limit strain as a core; then, through a particle swarm optimization algorithm, under a preset geometric constraint, taking a stability critical criterion as a boundary condition, carrying out multi-target iterative optimization calculation on the parameter set (L, S, H); and finally, outputting a target parameter group (Lf, Sf, Hf) which meets the critical stable state and has the optimal geometric dimension, and taking the target parameter group (Lf, Sf, Hf) as an optimal stable section solution. According to the method, automation and optimization of section design are achieved, the most economical and efficient cavern section shape can be sought on the premise that self-stabilization of surrounding rock is guaranteed, and the defects that a traditional design method depends on experience and is difficult to optimize are effectively overcome.

There is provided a method for designing a planar device comprising a carrier layer having an outer radius (RCout) and a carrier layer width (WC), a support layer having a support layer width (WS), a distance between an inner edge of the carrier layer and an inner edge of the support layer being (GAP), the method comprising obtaining predetermined values of RCout, WS and GAP; obtaining the geometrical shape of the mold; obtaining material characteristics of the supporting layer and the carrier layer; performing at least two simulations of thermoforming the planar device into a non-planar device based on the obtained predetermined values, the material characteristics and the geometry of the mold; determining a circumferential strain at an outer edge of a support layer of the simulated non-planar device; determining a linear relationship between the circumferential strain and a dimensional ratio defined by ratio = (WC-(WS + GAP)) / RCout based on the determined circumferential strain; determining a value of the dimensional ratio when the strain is zero based on the determined linear relationship; and determining the width of the carrier layer as WC = ratio * RCout + WS + GAP according to the dimensional ratio when the strain is zero.

A method for designing a flat device (100) to be thermoformed into a shape-retaining non-flat device (316) using a mold (214) is provided. The flat device comprises two concentric annular layers: a carrier layer (102), having an outer radius (Rcout) and a carrier layer width (Wc); and a support layer (104) having a support layer width (Ws). The support layer is mechanically attached to the carrier layer wherein an inner distance (GAP) is formed between an inner edge (106) of the carrier layer and an inner edge (108) of the support layer. The method comprises obtaining (1010) predetermined values for the outer radius of the carrier layer, the support layer width and the inner distance, obtaining (1020) a geometry of the mold, and obtaining (1030) material properties of the support layer and the carrier layer. The method further comprises performing (1040) at least two simulations of thermoforming a simulated flat device into a non-flat device using the mold, based on the obtained predetermined values, material properties, and geometry of the mold for at least two different carrier layer widths. The method further comprises determining (1050) a circumferential strain at an outer edge (314) of the support layer in each of the simulated non-flat devices. The method further comprises determining (1060), based on the determined circumferential strains, a linear relation (616) between the circumferential strain and a dimension ratio defined by ratio=WC−WS+GAP / RCout. The method further comprises determining (1070), based on the determined linear relation, a value (ratioMNB) of the dimension ratio for which the strain is zero and determining (1080), from the dimension ratio for which the strain is zero, the width of the carrier layer in the flat device as WC=ratio∗RCout+WS+GAP.